LOS ANGELES (Reuters) – Oscar-winning actress Gwyneth Paltrow on Wednesday was named the world's most beautiful woman for 2013 by People magazine, knocking pop singer Beyonce out of the top spot. The 40-year-old mother of two credits a five-day-a-week exercise regimen for keeping her in shape as she grows older. "It makes me look younger and feel strong," Paltrow told the magazine. "When I first started, I thought, 'I'll never be good at this. This is a nightmare!' But now it's like brushing my teeth, I just do it. …